The proposed research project explores the formation of concepts of human behavior by preschool children aged 2 1/2 to 6. The first objective of the research is to describe developmental changes in the child's use of information about another person's psychological state. The relevance of psychological information to the child's moral judgements, social judgements, and semantic judgements will be explored. The second objective of the project is to evaluate two alternative accounts of the failure to use psychological information at a given age. Does failure to use the information result from an inability to retain the formation or from a lack of perceived relevance of the information to the judgement?